The present invention relates to a paper feeder used together with a printer and a reader.
An automatic paper feeder generally has a hopper containing paper sheets to be fed into the paper feeder, and a feed roller arranged above the hopper. The hopper is urged toward the feed roller by a spring, and the uppermost sheet in the hopper is therefore urged against the feed roller. When the feed roller is driven in this state, sheets in the hopper are fed one by one into the apparatus, beginning with the uppermost sheet. When the uppermost sheet in the hopper is fed, however, the second and/or third sheets may also be fed into the apparatus with the uppermost sheet due to friction. For this reason, the paper feeder is provided with metal pawls to prevent feeding of the second and/or third sheets and to allow only the uppermost sheet to be fed into the printer.
In the paper feeder of the type described above, the hopper can contain a maximum of 50 to 100 sheets. When 100 or more sheets are set in the hopper, a spring having a large urging force must be used to urge the hopper upward. When such a strong spring is used, the uppermost sheet is urged against the feed roller with greater pressure as the number of sheets in the hopper decreases, necessitating that the feed roller be driven by a larger force and, consequently, that a larger drive motor be provided. Moreover, because the friction between sheets is increased by the pressure by which they are compressed, the problem of double feed or misfeed is all that much more prevalent.